import java.util.LinkedList;
import java.util.Queue;

class MyStackUsQueue {
    public Queue<Integer> queue1;
    public Queue<Integer> queue2;

    public void MyStack() {
        queue1 = new LinkedList<>();
        queue2 = new LinkedList<>();
    }

    public void push(int x) {
        if(empty()){
            queue1.offer(x);
        }else if(!queue1.isEmpty()){
            queue1.offer(x);
        }else{
            queue2.offer(x);
        }
    }

    public int pop() {
        if(empty()) {
            return -1;
        }
        if(!queue1.isEmpty()){
            int size = queue1.size();
            for(int i = 0 ; i < size-1 ; i++){
                queue2.offer(queue1.poll());
            }
            return queue1.poll();
        }else{
            int size = queue2.size();
            for(int i = 0 ; i < size-1 ; i++){
                queue1.offer(queue2.poll());
            }
            return queue2.poll();
        }
    }

    public int top() {
        if(empty()) {
            return -1;
        }
        int ret = -1;
        if(!queue1.isEmpty()){
            int size = queue1.size();
            for(int i = 0 ; i < size ; i++){
                ret = queue1.poll();
                queue2.offer(ret);
            }
            return ret;
        }else{
            int size = queue2.size();
            for(int i = 0 ; i < size ; i++){
                ret = queue2.poll();
                queue1.offer(ret);
            }
            return ret;
        }
    }

    public boolean empty() {
        return queue1.isEmpty() && queue2.isEmpty();
    }
}